Method and apparatus for perforating a fibrous web

ABSTRACT

A method and apparatus are disclosed for forming a pattern of low basis weight regions, such as apertures or perforations, in an unbonded fibrous web. The present apparatus includes a forming surface having a pattern of forming elements, with an unbonded web positioned in operative association with the forming surface. Differential air pressure is applied to the web so that a pattern of low basis weight regions is formed corresponding to the pattern of forming elements. The fibrous web is thereafter removed from the forming surface, and can be further processed, if desired, such as by application of binders or other finishes, and can be integrated with associated components for various end uses, including medical, industrial, and hygiene applications.

TECHNICAL FIELD

The present invention generally relates to a method and apparatus for perforating, or otherwise forming regions of low basis weight, in a fibrous web, and more particularly relates to a method and apparatus for perforating an un-bonded fibrous web suited for products in medical, industrial, and hygiene applications.

BACKGROUND OF THE INVENTION

Perforated nonwoven webs have found use in various applications where a need exits for the transport of gases and fluids. Perforations may be imparted to a fibrous web by screens that have raised portions throughout, as described in U.S. Pat. No. 5,785,697, entitled, “Absorbent Composite Web”, issued Jul. 28, 1998 to inventors Trombetta, et al. As fibers are laid down on the screen the fibers circumscribe the raised portions projecting from the surface of the screen, apertures are formed within the web. Depending on the size and three-dimensional shape of the raised portions projecting from the screen, associated apertures may be of various shapes and sizes.

In an alternate perforating method, a forming screen and transfer surface is employed. The forming screen includes a nob, which may also take the form of various shapes. The method as described in U.S. Pat. No. 6,220,999, entitled, “Method And Apparatus For Forming An Apertured Pad”, issued Apr. 24, 2001 to inventors Kugler, et al., includes a rotatable forming screen having a series of projections, referred to as “nobs”, wherein the nobs may be re-attachable to the screen by using threaded fasteners. Material is deposited on the forming screen, circumscribing the nobs to form an absorbent pad.

In yet another method for imparting perforations into a fibrous web includes perforating the web between a pair of compression rolls. U.S. Pat. No. 5,242,435, entitled, “Highly Absorbent And Flexible Cellulosic Pulp Fluff Sheet”, issued on Sep. 7, 1993 to inventors Murji, et al, discloses a “perf-embossing” method involving a calendaring station. The fibrous web may be subjected to various ranges of pressures between two rolls including teeth to perforate the web. A subsequent step further embosses the web.

SUMMARY OF THE INVENTION

The present invention is directed to a method and apparatus for perforating, or otherwise forming regions of low basis weight, in an un-bonded fibrous web suited for products in medical, industrial, and hygiene applications. A method of forming a fibrous web with a pattern of low basis weight regions in accordance with the present invention, comprises the steps of providing a substantially continuous fibrous web comprising fibrous and/or filamentary material. The method further comprises providing a forming surface defining a pattern of forming elements, and directing the fibrous web onto the forming surface. The present method contemplates applying differential air pressure to the web to displace material therefrom to form a pattern of low basis weight regions in the web corresponding to the pattern of forming elements on the forming surface. Thereafter, the fibrous web is removed from the forming surface, and can be further processed, if desired, such as by application of binders or other finishes, and can be integrated with associated components for end uses.

In one embodiment of the present invention, the forming surface is provided in the form of a cylindrical forming drum, wherein the forming elements comprise a pattern of openings defined by the drum. In order to direct the fibrous web onto the drum, a flexible, foraminous belt is provided, with the fibrous web positioned between the belt and the forming drum.

Differential air pressure is applied to the web by drawing a vacuum from within the drum through the pattern of openings, to thereby displace fibrous material from the web, to form the pattern of low basis weight regions. In this embodiment, it is further contemplated that pressurized air can be directed through the foraminous belt and the fibrous web, and into the pattern of openings of the forming drum, thus further facilitating formation of low basis weight regions/perforations in the fibrous web.

It is additionally contemplated that pressurized air can be directed from within the forming drum, through the pattern of openings, after the vacuum has been drawn from within the drum through the pattern of openings therein. Alternately, this embodiment can be operated without creating a vacuum within the drum, but instead by directing pressurized air from within the drum through the pattern of openings to displace fibrous material from the web, thereby forming the desired low basis weight regions.

In an alternate embodiment of the present invention, a forming surface of the apparatus is provided in the form of a foraminous forming drum, wherein the pattern of forming elements comprises a pattern of upstanding projections on the periphery of the forming drum. Operation of this embodiment contemplates that differential air pressure is applied to the fibrous web of material by drawing a vacuum from within the drum so that the fibrous web inter-engages the pattern of projections, to thereby form the desired pattern of low basis weight regions/perforations corresponding to the pattern of projections.

In one form of this embodiment of the invention, the apparatus includes a cooperating female sleeve, positioned in operative association with the forming drum, and defining a pattern of recesses corresponding to the pattern of projections on the forming drum. The projections are received in the recesses with the fibrous web positioned between the forming drum and the female sleeve, to thereby form the desired pattern of low basis weight regions/perforations. In this form of the invention, it is contemplated that pressurized air can be directed from within the female sleeve against the fibrous web to further facilitate the desired displacement of material for formation of the desired low basis weight regions.

In a further embodiment of the present invention, the forming surface is provided in the form of a foraminous belt, with the pattern of forming element comprising a pattern of relatively high-flow regions defined by the belt. Differential air pressure is applied to the fibrous web positioned on the belt by directing air pressure against the fibrous web and through the foraminous belt, and or by drawing a vacuum through the foraminout belt. In this fashion, the desired pattern of low basis weight regions, corresponding to the pattern of high-flow regions defined by the belt, is formed.

In an alternate embodiment, the forming surface is provided in the form of a foraminous belt, with the pattern of forming elements comprising a pattern of relatively low-flow regions defined by the belt. After disposition of the fibrous web on the foraminous belt, air is directed against the web and through the foraminous belt to form the pattern of low basis weight regions therein corresponding to the pattern of low-flow regions defined by the belt. As in the previous embodiment, the step of directing air pressure against the fibrous web can be provided by drawing a vacuum through the foraminous belt. In this embodiment, the low-flow regions defined by the foraminous belt are substantially impermeable.

According to the present invention, a perforated web is formed by controlling airflow through the un-bonded web and apparatus. The method of making a perforated web is particularly suited for constructing layered products, such as spunmelt constructs. Other features and advantages of the present invention will become readily apparent from the following detailed description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of an apparatus for practicing the method of the present invention;

FIG. 2 is a further diagrammatic view of the apparatus shown in FIG. 1;

FIG. 3 is a partial, diagrammatic view illustrating a foraminous forming drum of the apparatus shown in FIGS. 1 and 2;

FIG. 4 is a diagrammatic view of an alternate form of the apparatus shown in FIGS. 1-3;

FIG. 5 is a diagrammatic view of an alternate apparatus for practicing the method of the present invention;

FIG. 5 a is a view of an aperture-forming projection of the apparatus shown in FIG. 5; and

FIGS. 6 a and 6 b are diagrammatic views illustrating further embodiments of an apparatus for practicing the method of the present invention.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

With reference to FIG. 1, therein is illustrated an apparatus 10 for practicing the method of the present invention, wherein un-bonded fibrous webs are formed to define perforations or apertures, or otherwise low basis weight regions. In accordance with the present invention, the fibrous webs are intended to encompass those webs formed from natural and/or synthetic fibers, and/or filamentary elements, such as spunbond filaments. This embodiment of the present invention is particularly suited for processing fibrous webs comprised of relatively short fibers, typically 1-10 millimeters in length, with the present process contemplating extracting and/or blowing fibers from non-trapped regions of the fibrous webs, while other portions of the fibrous webs are retained or trapped in captive relationship between a foraminous forming belt and an associated foraminous forming drum, which defines a pattern of openings or perforations. As will be further described, this pattern of openings or perforations in the foraminous drum effects formation of a like pattern of low basis weight regions in the associated fibrous web.

In accordance with this embodiment of the invention, apparatus 10 includes an air laying unit 12, which cooperates with an associated suction box 14 for formation of a fibrous web F on an associated flexible, foraminous forming belt 16. Forming belt 16 is preferably of relatively fine mesh, and may be formed from either metallic or synthetic material. User of synthetic polymeric-type materials is presently preferred.

The open surface area of the foraminous bent 16 is preferably between 15 and 70 percent, with a range of 25-45 percent presently being preferred. The foraminous belt may have a mesh count of 5-15 elements per centimeter, with nine elements per centimeter presently preferred. The foraminous belt may exhibit a smooth surface, plain weave, or twill, or other weave that facilitates maximum contact with the associated fibrous web F. This foraminous belt should exhibit an air permeability on the order of 650-6500 l/m²/s. Typical suppliers include GKD (Gebr. Kuferath AG) Type 40565610 or Villforth Kunststof Bonderbelt—Powerflex 4 schaft PES.

In accordance with the present invention, apparatus 10 further includes a forming surface which defines a pattern of forming elements, which pattern corresponds to the pattern of low basis weight regions to be formed in the fibrous web F. In this embodiment, the forming surface is provided in the form of a cylindrical foraminous forming drum 18 which defines a pattern of openings (i.e., apertures or perforations) with the drum cooperating with the foraminous belt 16 to form the desired pattern of low basis weight regions in the associated fibrous web F. Drum 18 can be driven by belt 16, or otherwise operated for synchronous movement therewith.

The foraminous forming drum 18 can be suitably formed from metallic or polymeric material, with the drum provided with a wall thickness from about 1 millimeter to about 10 millimeters, depending upon the material from which the drum is formed. It is presently preferred that the thickness be between about 3-6 millimeters. Formation of the drum from screen or perforated material, or in the form of an image transfer device (ITD) having an ablated surface, is within the purview of the present invention.

The open area of the forming drum 18 depends on the pattern/desired requirements for the patterned fibrous web which is being formed. It is contemplated that the open area of the forming drum can be varied from about 10% to about 75%, with the preferred open area being from about 25% to about 45%. The drum diameter may range from about 300 millimeters to about 1500 millimeters, with a diameter on the order of about 500 millimeters presently being preferred.

In accordance with the present invention, fibrous web F is directed onto the forming surface of forming drum 18, with differential air pressure applied to the web to displace material therefrom to form the desired pattern of low basis weight regions therein. In this embodiment, processing of the fibrous web in this fashion is facilitated by positioning the fibrous web on the foraminous belt 16, and thereafter positioning the web between the belt and the exterior surface of the forming drum 18. Thus, the forming drum and foraminous belt cooperate to retain the fibrous web in trapped or captive relationship so that the fibrous web can be subjected to differential air pressure for effecting formation of the desired pattern or low basis weight regions.

In the embodiment of the apparatus illustrated in FIGS. 1-3, differential air pressure is applied to the fibrous web F by drawing a vacuum from within forming drum 18 through the pattern of openings defined in its forming surface, to thereby displace fibrous material from the web, and form the desired pattern of low basis weight regions. To this end, a fixed position vacuum head 20 is provided within the forming drum 18. It is presently contemplated that the vacuum head be fixed to operate over an arc of 45° within the forming drum 18, but this can be varied depending upon the desired forming pattern and speed of operation of the apparatus. The angle of the vacuum head is preferably positioned such that vacuum is applied to the fibrous web F after it is held in captive relationship between foraminous belt 16 and forming head 18. The vacuum drawn by the vacuum head 20 can be varied to be greater than −150 mbar, and less than −10 mbar, depending upon the speed, opening of the pattern of openings in the forming drum 18, the mesh/opening of the restraining foraminous belt 16, and the setting of the associated diverting plates.

In this regard, apparatus 10 includes an air diverting plate 22, positioned generally in operative association with the vacuum head 20, generally at the exterior of foraminous belt 16. The air diverting plate 22 can be configured in the nature of an adjustable blind or baffle, including a plurality of adjustable slats whereby speed and direction of air directed through the foraminous belt 16 and against the fibrous web F can be selectively controlled.

As illustrated in FIG. 3, apparatus 10 further includes an arrangement for directing pressurized air from within forming drum 18 through the pattern of openings therein, and against the fibrous web F. This arrangement includes an air-blowing device 24 positioned within the forming drum, with the preferred arrangement further including a deflector 26 positioned in operative association with the blowing device 24 exteriorly of the forming drum 18.

The provision of blowing device 24 desirably acts to improve the clarity of perforations or apertures formed in fibrous web F by directing pressurized air to the perforated areas after the application of suction from vacuum head 20. Typically, compressed air is directed through the blowing device, with the provision of the blowing device desirably acting to ensure that the perforated fibrous web F is laying on the foraminous belt 16, thus facilitating separation of the fibrous web F from the forming drum 18. It is contemplated that blowing device 24 can be operated at a pressure between about 0.5 bar to about 15 bar, per blowing element. While the minimum number of blowing elements, or jet rolls, is one, depending upon the weight of the fibrous web and desired hole design, a plurality of the jet rolls may be required to achieve the desired level of aperture clarity. While space limitations within the foraminous drum 18 can limit the number of jet rolls of the blowing device, it is presently contemplated that 2-4 of the jet rolls can be provided within the foraminous drum 18.

Air deflector 26 preferably cooperates with the blowing device 24, with the deflector exhibiting a diamond-shaped surface deflector opposite the jet rolls of the blowing device 24. The deflector is intended to function to maximize the performance of air directed from the blowing device 24, with the gap of the deflector to the forming drum 18, the perforated web F, and the foraminous belt 16 being adjustable to maximize the required effect of web transfer, hole clarity and/or profile surface around the fibrous web.

FIG. 4 illustrates an alternate embodiment of this form of the present apparatus, wherein a blowing device 24 is positioned within forming drum 18, with only the compressed air delivered by the blowing device acting to create the desired low basis weight regions in the associated fibrous web F. As will be observed, this embodiment of the present invention does not include an arrangement for drawing a vacuum from within the forming drum 18, but rather can include a plurality of nozzles or slots from which air is delivered, through the pattern of openings in the forming drum 18, for cooperation with the exterior deflector 26. Thus, this embodiment of the present invention acts to direct pressurized air from within the forming drum 18 through the pattern of openings defined thereby to displace fibrous material from the fibrous web F, to thereby form the desired pattern of low basis weight regions (e.g., perforations or apertures) in the fibrous web F.

With reference to FIG. 5, therein is illustrated an alternate embodiment for practicing the method of the present invention, whereby a fibrous web F is provided with a pattern of low basis weight regions (e.g., apertures, perforations), again by applying differential air pressure to the web to displace material to form the desired pattern therein. This embodiment includes a forming surface in the form of a foraminous forming drum 28, wherein the forming surface includes a pattern of forming elements in the form of a pattern of upstanding projections 30 on the periphery of the forming drum 28. It is contemplated that this form of apparatus for practicing the present invention is particularly suited for carded fibrous webs, with fiber lengths from about 10 to about 100 millimeters, and is also suitable for processing non-bonded spun-melt webs, and may also be suitable for use in processing webs formed from short fibers delivered by air-former systems, or combinations thereof.

The projections 30 provided about the periphery of foraminous drum 28 are preferably provided in a generally tapered configuration, and may be provided with a helical recess 31 machined into the external surface of the projections (see FIG. 5 a).

As the fibrous web F is directed onto the forming surface of foraminous forming drum 28, differential air pressure is applied thereto by drawing a vacuum from within the drum by the provision of a vacuum head 32 positioned within the drum 28. By this arrangement, the fibrous web interengages the pattern of projections 30 on the drum to form the desired pattern of low basis weight regions, especially perforations or projections, corresponding to the pattern of projections 30.

In order to ensure the desired clarity of apertured formed in the fibrous web F, it is presently preferred that this embodiment of the present apparatus includes a female sleeve 34, positioned in operative association with the forming drum, and which cooperates with forming drum 28, such that the fibrous web F is directed between the forming drum 28 and the female sleeve 34. The sleeve defines a pattern of recesses or apertures corresponding to the pattern of projections 30 on the drum 28, such that the projections are received in the recesses when the fibrous web is positioned between the forming drum and the female sleeve to form the desired pattern of low basis weight regions in the form of apertures or perforations. The provision of the female sleeve 38 is believed to be particularly desirable for processing relatively heavy weight staple fiber webs, as well as webs formed from spun-melt materials. In this regard, it is particularly preferred to direct pressurized air from within the female sleeve against the fibrous web, with an air slot 36 provided within the sleeve 34 for this purpose.

Features of the embodiment illustrated in FIG. 5 facilitate its efficient operation for handling fibrous webs of varying characteristics. The foraminous forming drum 28 may include a suitable internal supporting frame for the internal circumference thereof, with the exterior fine mesh screen pre-mounted with the desired projections 30, preferably in the form of the afore-described helically-grooved pins. While metallic mesh screen is presently preferred for this application, it is within the purview of the present invention that a synthetic polymeric-type mesh may be employed, or a combination of polymer and metallic-types. One screen found to be suitable for this application is type ND 20 from GKD (Gebr. Kufferath AG). The ND 20 screen has a 31 warp by 20 weft with wire thickness of 0.18 mm by 0.205 mm, exhibiting an air permeability of 7400 l/m²/s.

As noted, the screen for the foraminous drum can be pre-mounted with the projections 30, but it is also possible that the projections can be mounted on the internal supporting frame for the drum, with the exterior screen provided with openings through which the pins project. While it is contemplated that the projections 30 be provided in the form of helically-grooved pins, as illustrated in FIG. 6 a, it will be understood that a similar effect can be achieved with non-grooved pins.

In this regard, the pins which provide projections 30 are designed to have a helical or spiral shape to facilitate the unbonded fibrous web F to be perforated with clear openings during processing. In particular, the fibers around the helically-grooved projections 30 are desirably twisted around during the perforation process.

Suitable material for the projections 30 include metallic and synthetic polymeric materials, or combinations thereof. Because the fibrous material of the web F is unbonded, it has been found that forming the projections from synthetic material is presently preferred, since such materials typically exhibit lower friction than metallic materials.

It should be noted that the pins which provide projections 30 on the forming drum 28 can be a combination of different diameters, with preferred diameters being in the range from about 8 mm to about 25 mm. The projections 30 can protrude to a height from about 5 mm to about 25 mm, depending on the weight of the unbonded fibrous web F, with the preferred height being on the order of about 7 mm to about 12 mm.

The vacuum head 32 positioned within the foraminous forming drum 28 can be operated to provide a vacuum level between about −150 mbar, and about −10 mbar, depending on the speed of operation, fiber cohesion, types of webs and web weight, fiber length, or continuous filaments, etc.

As noted, the provision of female sleeve 34 is particularly desirable for processing relatively heavy fibrous webs, and webs formed from melt-spun elements. It is also believed that the provision of female sleeve 34 can be desirable for processing lighter weight webs which exhibit good fiber adhesion. The provision of air slot 36 within the female sleeve 34 facilitates formation of perforations in the fibrous web, particularly if the fibrous web is partially positioned on the projections 30, and not fully seated on the foraminous surface of drum 28.

In the preferred form, a tension/vacuum transfer roll 38 is provided upstream of the forming drum 28, and desirably ensures that sufficient tension is created in the fibrous web to facilitate the perforation which is effected of the unbonded fibrous web by the action of the projections 30 on the foraminous forming drum 28. Roll 38 also desirably acts to facilitate transfer of the fibrous web F from the associated transfer belt positioned upstream of the perforation apparatus.

In the illustrated embodiment, another tension/vacuum roll 40 is provided positioned downstream of the foraminous forming drum 28. This roll facilitates removal of the now-perforated web from the drum 28, such as for integration with associated components of a composite structure.

FIGS. 6 a and 6 b illustrate a further apparatus for practice of the present invention, with this embodiment including a forming surface defining a pattern of forming elements in the form of a foraminous belt which exhibits regions of relatively high and low air flow.

FIG. 6 a illustrates an embodiment of a forming surface which can be formed by integrating two foraminous or mesh belts with each other so as to form a composite belt structure 42 exhibiting a pattern of relatively low-flow regions, which pattern corresponds to the pattern of low basis weight regions to be formed in an associated fibrous web. To this end, the “dual belt” structure can be formed by providing a normal fine mesh belt of substantially continuous configuration, with another fine mesh belt, having either a finer or coarser mesh, with the second belt including cut-out regions or openings. The integrated belt structure 42 thus defines regions of relatively high-flow corresponding to the cut-out regions of the second mesh belt. In this embodiment, differential air pressure is applied to the associated fibrous web, such as by drawing a vacuum through the composite foraminous belt structure.

In the embodiment of FIG. 6 b, a forming surface in the form of a foraminous belt 44 is provided with a pattern of forming elements 46 which comprise a pattern of low-flow regions defined by the foraminous belt. Formation of this belt is effected by covering/welding, or otherwise coating the desired pattern on the foraminous surface of the belt, again with differential air pressure applied to the associated web such as by drawing a vacuum through the foraminous belt. In this embodiment, it is contemplated that the low-flow regions defined by the foraminous belt are substantially impermeable, such as by securing polymeric elliptical elements 46 to the foraminous belt. By this arrangement, attendant to application of differential air pressure to a fibrous web positioned on the belt, the desired pattern of low basis weight regions is formed in the web, with the pattern corresponding to the pattern of low-flow regions of the foraminous belt.

Fibrous webs exhibiting a pattern of low basis weight regions formed in accordance with the present invention can be advantageously employed in a wide variety of applications. Apertures/perforated areas in cellulose-based carded webs or air-formed webs, or combinations thereof, are particularly suitable as a “sandwich” layer in between associated spun-melt constructions, or as part of a spun-melt construction to provide absorbent regions, and relatively less absorbent regions, from the perforated areas, for extra breathability, and dry-feeling comfort in apparel applications. Such a construction can be particularly suitable for medical protection articles, such as caps, isolation gowns, scrub suits, drapes, and the like.

It will be noted that multi-layered composite constructions can be provided with non-continuous layers of cellulose-based fibrous webs positioned between associated spunbond (S) and meltblown (M) webs. In a construction wherein such a cellulose-based web is positioned between associated spunbond layers, a composite structure is provided which is particularly suited for surgical scrub suits and caps, as well as for general-purpose applications, in view of the desired enhancement of wearer comfort provided by the liquid repellant but well-ventilated properties of the composite construction.

The provision of a cellulose-based fibrous web formed in accordance with the present invention in association with plural spunbond and meltblown layers can be particularly suitable for use in medical applications, as well as for special industrial applications where it is desired to reduce static characteristics is low humidity environments.

A medical drape material formed from a composite including a non-continuous cellulose-based web, formed in accordance with the present invention, positioned in association with meltblown and spunbond layers can be designed such that a spunbond layer configured to exhibit hydrophilicity can be positioned next to the cellulose-based fibrous web formed in accordance with the present invention.

Bonded fabrics, with one side exhibiting a profile shape, made from a combination of layer or layers of a perforated web, and layer or layers of non-perforated webs, can deliver specific delayed liquid run-off properties, as can be desirable for medical-drape fabrics. Bonded fabrics from two or more layers of perforated webs formed in accordance with the present invention can be provided with low basis weight, open areas, which are non-aligned on opposite surfaces, to thus deliver unique features for application such as wipes, as well as hygiene, medical, and industrial applications.

Apertures and perforations formed in spun-melt composite constructs, before bonding, can also provide unique properties for medical devices, and applications such as wipes, hygiene products, and industrial products.

From the foregoing, it will be observed that numerous modifications and variations can be effected without departing from the true spirit and scope of the novel concept of the present invention. It is to be understood that no limitation with respect to the specific embodiment illustrated herein is intended or should be inferred. The disclosure is intended to cover, by the appended claims, all such modifications as fall within the scope of the claims. 

1. A method of forming a fibrous web with a pattern of low basis weight regions, comprising the steps of: providing a substantially continuous fibrous web comprising fibrous and/or filamentary material; providing a forming surface defining a pattern of forming elements; directing said fibrous web onto said forming surface; applying differential air pressure to said web to displace the material thereof to form a pattern of low basis weight regions in said web corresponding to said pattern of forming elements of said forming surface; and removing said fibrous web from said forming surface.
 2. A method of forming a fibrous web in accordance with claim 1, wherein: said forming surface comprises a forming drum, wherein said pattern of forming elements comprises a pattern of openings defined by said drum.
 3. A method of forming a fibrous web in accordance with claim 2, wherein: said directing step includes positioning said fibrous web on a flexible, foraminous belt, and positioning said web between said belt and said forming drum.
 4. A method of forming a fibrous web in accordance with claim 3, wherein: said applying step includes drawing a vacuum from within said drum through said pattern of openings to displace fibrous material from said web to form said pattern of low basis weight regions.
 5. A method of forming a fibrous web in accordance with claim 4, wherein: said applying step further includes directing pressurized air through said foraminous belt and said fibrous web, and into said pattern of openings of said forming drum.
 6. A method of forming a fibrous web in accordance with claim 4, wherein: said applying step further includes directing pressurized air from within said forming drum through said pattern of openings after drawing said vacuum through said pattern of openings.
 7. A method of forming a fibrous web in accordance with claim 3, wherein: said applying step includes directing pressurized air from within said drum through said pattern of openings to displace fibrous material from said web to form said pattern of low basis weight regions.
 8. A method of forming a fibrous web in accordance with claim 1, wherein: said forming surface comprises a foraminous forming drum, wherein said pattern of forming elements comprises a pattern of upstanding projections on the periphery of said forming drum, said applying step including applying differential pressure to said web of fibrous material by drawing a vacuum from within said drum so that said web inter-engages said pattern of projections to form said pattern of low basis weight regions corresponding to said pattern of projections.
 9. A method of forming a fibrous web in accordance with claim 8, including: providing a cooperating female sleeve positioned in operative relationship with said forming drum and defining a pattern of recesses corresponding to said pattern of projections, so that said projections are received in said recesses with said fibrous web positioned between said forming drum and female sleeve to form said pattern of low basis weight regions.
 10. A method of forming a fibrous web in accordance with claim 9, wherein: said applying step further includes directing pressurized air from within said female sleeve against said fibrous web.
 11. A method of forming a fibrous web in accordance with claim 1, wherein: said forming surface comprises a foraminous belt, and said pattern of elements comprises a pattern of relatively high-flow regions defined by said belt, said applying step including directing air against said fibrous web and through said foraminous belt to form said pattern of low basis weight regions corresponding to said pattern of high-flow regions defined by said belt.
 12. A method of forming a fibrous web in accordance with claim 11, wherein: said applying step includes drawing a vacuum through said foraminous belt.
 13. A method of forming a fibrous web in accordance with claim 1, wherein: said forming surface comprises a foraminous belt, and said pattern of elements comprises a pattern of relatively low-flow regions defined by said belt, said applying step including directing air against said fibrous web and through said foraminous belt to form said pattern of low basis weight regions corresponding to said pattern of low-flow regions defined by said belt.
 14. A method of forming a fibrous web in accordance with claim 13, wherein: said low-flow regions defined by said foraminous belt are substantially impermeable.
 15. A method of forming a fibrous web in accordance with claim 13, wherein: said applying step includes drawing a vacuum through said foraminous belt.
 16. An apparatus for forming a fibrous web with a pattern of low basis weight regions, comprising: a forming surface defining a pattern of forming elements; and an arrangement for applying differential air pressure to a web of fibrous material, comprising fibrous and/or filamentary material, when said web is positioned on said forming surface to form a pattern of low basis weight regions corresponding to said pattern of forming elements.
 17. An apparatus for forming a fibrous web in accordance with claim 16, wherein: said forming surface comprises a forming drum, wherein said pattern of forming elements comprises a pattern of openings defined by said drum.
 18. An apparatus for forming a fibrous web in accordance with claim 17, including: a flexible, foraminous belt positioned in operative association with said forming drum for positioning said web of fibrous material between said foraminous belt and said forming drum.
 19. An apparatus for forming a fibrous web in accordance with claim 18, wherein: said arrangement for applying differential air pressure to said web of fibrous material comprises an arrangement for drawing a vacuum from within said drum through said pattern of openings to displace fibrous material from said web to form said pattern of low basis weight regions.
 20. An apparatus for forming a fibrous web in accordance with claim 19, wherein: said arrangement for applying differential fluid pressure to said web of fibrous material further comprises an arrangement for directing pressurized air through said foraminous belt and said web of fibrous material, and into said pattern of opening in said forming drum.
 21. An apparatus for forming a fibrous web in accordance with claim 19, wherein: said arrangement for applying differential air pressure further includes an arrangement for directing pressurized air from within said forming drum through said pattern of openings after drawing said vacuum through said openings.
 22. An apparatus for forming a fibrous web in accordance with claim 18, wherein: said arrangement for applying differential air pressure to said web of fibrous material comprises a arrangement for directing pressurized air from within said drum through said pattern of openings to displace fibrous material from said web to form said pattern of low basis weight regions.
 23. An apparatus for forming a fibrous web in accordance with claim 16, wherein: said forming surface comprises a foraminous forming drum, wherein said pattern of forming elements comprises a pattern of upstanding projections on the periphery of said forming drum, said arrangement for applying differential pressure to said web of fibrous material comprising an arrangement for drawing a vacuum from within said drum so that said web inter-engages said pattern of projections to form said pattern of low basis weight regions corresponding to said pattern of projections.
 24. An apparatus for forming a fibrous web in accordance with claim 16, including: a cooperating female sleeve positioned in operative relationship with said forming drum, and defining a pattern of recesses corresponding to said pattern of projections, so that said projections are received in said recesses with said fibrous web positioned between said forming drum and female sleeve to form said pattern of low basis weight regions.
 25. An apparatus for forming a fibrous web in accordance with claim 24, wherein: said forming surface comprises a foraminous belt, and said pattern of elements comprises a pattern of relatively high-flow regions defined by said belt, said arrangement for applying differential air pressure comprising an arrangement for directing air pressure against said fibrous web and through said foraminous belt to form said pattern of low basis weight regions corresponding to said pattern of high-flow regions defined by said belt.
 26. An apparatus for forming a fibrous web in accordance with claim 24, wherein: said arrangement for applying differential air pressure further comprises an arrangement for drawing a vacuum through said foraminous belt.
 27. An apparatus for forming a fibrous web in accordance with claim 24, wherein: said forming surface comprises a foraminous belt, and said pattern of elements comprises a pattern of relatively low-flow regions defined by said belt, said arrangement for applying differential air pressure including an arrangement for directing air against said fibrous web and through said foraminous belt to form said pattern of low basis weight regions corresponding to said pattern of low-flow regions defined by said belt.
 28. An apparatus for forming a fibrous web in accordance with claim 27, wherein: said low-flow regions defined by said foraminous belt are substantially impermeable.
 29. An apparatus for forming a fibrous web in accordance with claim 27, wherein: said arrangement for applying differential air pressure further comprises an arrangement for drawing a vacuum through said foraminous belt. 